• Journal of Pharmaceutical Investigation
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• v.11 no.3
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• pp.1-13
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• 1981

A new application of monoacidic dye is reported for the determination of pipethanate hydrochloride(PTH). The method is based on solvent extraction into chloroform of an ion-pair compound formed between methyl orange(MO) and PTH. PTH is determined by measuring absorbance of the extracts over the range of $2.0{\sim}12.0{\mu}g/ml$ at 420nm. Best accuracy can be obtained for solutions containing $3.0{\sim}8.0{\mu}g/ml$. The color was stable for at least 5 days. The molar absorptivity was $2.88\;{\times}\;10^4\;l,\;mol^{-1},\;cm^{-1}$. Molar ratio and continuous variation plots have a maximum at 0.5 mol fraction of MO, indicating a 1 : 1 MO-PTH ratio.

• YAKHAK HOEJI
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• v.22 no.1
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• pp.27-32
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• 1978

Metoclopramide reacts with ammonium cobaltothiocyanate to form a stable ion pair which has an absorption maximum of 625mm. The reaction product was insoluble in water but soluble in most organic solvents. 1,2-Dichlorethane was the best extracting solvent among the several organic solvents tested. Metoclopramide can be determinded not only by visible light spectrophotometry but also indirectly by estimation of cobalt in the organic phase by flameless atomic absorption spectrophotometry. Linear relationship was found between absorbance and concentration in the range of 10$^{-4/}$-10$^{-3}$M by spectrophotometry and 10$^{-5}$-10$^{-4}$M by flameless atomic absorption spectrophotometry. The coefficient of variation by spectrophotometry was 0.9% and that of flameless atomic absorption was 1.8%. There was no interference with excipients, pH, temperature and reaction time. With this method, it is possible to determine accurately metoclopramide and tertiary amines in pharmaceutical preparations.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4179-4184
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• 2011

The nucleophilic substitution reactions of bis(2,6-dimethylphenyl) chlorophosphate (5), containing the four ortho-methyl substituents, with X-pyridines are investigated kinetically in MeCN at $65.0^{\circ}C$. The free energy correlations for substituent X variations in the nucleophiles exhibit biphasic concave upwards with a breakpoint at a X = 3-Cl. Unusual positive ${\rho}_X$ (= +5.40) and negative ${\beta}_X$ (= -0.83) values are obtained with the weakly basic pyridines. The pyridinolysis rate of 5 is hundreds times slower compared to that of bis(phenyl) chlorophosphate because of the steric hindrance of the four ortho-methyl substituents in the two phenyl rings. Ion-pair mechanism is proposed and positive ${\rho}_X$ and negative ${\beta}_X$ values are substantiated by an imbalance of the transition state.

• YAKHAK HOEJI
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• v.38 no.4
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• pp.379-388
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• 1994

A new method for the analysis of metocurine iodide in biological fluids was developed. Metocurine iodide was quantitatively extracted with rose bengal from aqueous layer into dichloromethane layer and the amount of metocurine iodide was calculated from the amount of rose bengal which was determined by HPLC with fluorescence detector. It was possible to analyze metocurine iodide without the effect of co-prescribed drugs in the concentration range of $0.09{\sim}9.10\;{\mu}g/ml$. The detection limits of metocurine iodide in urine and blood were 0.8 and 1.2 ng at S/N=3, each respectively.

• Archives of Pharmacal Research
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• v.27 no.6
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• pp.670-675
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• 2004

Since the bitter taste of enrofloxacin apparently limit the patient compliance in the oral formulations of the antibacterial agent, the masking of the taste is essential for the improvement of the therapeutic effectiveness. Therefore, this study was carried out to examine the feasibility of taste masking of enrofloxacin by the retardation of its dissolution rate using the formation of complex between the drug and Carbopol. The complexation between Carbopol and enrofloxacin was confirmed by turbidity, UV spectrophotometry, wide angle X-ray diffraction, and differential scanning calorimetry. The enrofloxacin content in the complexes was 34％ （Carbo-enrofloxacin complex I） and 57％ （Carbo-enrofloxacin complex II） depending on the prepara-tion method. The dissolution rate of enrofloxacin from the complex increased as the pH was reduced. The dissolution rate of enrofloxacin from the Carbo-enrofloxacin complex I was significantly lower than that of the enrofloxacin powder. Therefore, these observations suggest that Carbo-enrofloxacin complex I can be used to mask the taste of enrofloxacin.

• Archives of Pharmacal Research
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• v.17 no.6
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• pp.415-419
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• 1994

A simple nad rapid colorimetric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate is described. The method is based on the interaction of the drug base with bromophenol blue to give a ion-pair complex. The spectra of the complex shows a maxima at 415-420 nm with high apparent molar absorptivities. Beer's law was obeyed in the concentration range 1-8, 2-10 and $2-12{\;}{\mu}{\cdot}ml^{-1}$ for amodiaquine hydrochloride, primaquine phosphate and chloroquine phosphate respectively. The proposed method was applied to the determination of these drugs in certain formulations and the results were favourably comparable to the official methods.

• YAKHAK HOEJI
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• v.27 no.4
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• pp.303-307
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• 1983

Pipethanate*HCl reacts with ammonium cobaltothiocyanate to form a stable ion pair which has an absorption maximum at 626nm. The reaction product was insoluble in water but freely soluble in most organic solvents. 1, 2-Dichloroethane was the best extracting solvent among the several organic solvents. Pipethanate*HCl can be determined not only by the spectrophotometry but also inderectly by estimation of cobalt in the organic phase by atomic absorption spectrophotometry. Linear relationship was found between absorbance and concentration in the range of $1.0{\times}10^{-3}~4.0{\times}10^{-3}M$ by spectrophotometry and $1.5{\times}10^{-4}~4.0{\times}10^{-4}M$ by atomic absorption spectrophotometry. With this method it was possible to determine pipethanate$\cdot$HCl in the pharmaceutical preparations.

• Bulletin of the Korean Chemical Society
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• v.5 no.3
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• pp.112-117
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• 1984

The association constants (K) of 3,5,N-trimethyl pyridinium iodide in 95 volume percent ethanol-water mixed solvent were determined by a modified UV and conductance method at $25^{\circ},\;30{\circ},\;40{\circ}\;and\;50{\circ}C$ over the pressure range 1 to 2000 bars. The association process is enhanced with increasing pressure and decreasing temperature. From K values, we obtained the total partial molar volume change (${\Delta}V$) and some thermodynamic parameters. The electrostriction volume (${\Delta}V_{el}$) and intrinsic volume (${\Delta}V_{in}$) were also evaluated. The values of ${\Delta}V,\;{\Delta}V_{el},\;{\Delta}V_{in}$ are negative, negative and positive, respectively, and the absolute values of all these three decrease with increasing pressure and temperature. The ion-pair size (a) were varied 3 to 6 ${\AA}$, with pressure and temperature. The solvation number (n) decreased from 2 to 0.5 with increasing temperature.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.17-20
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• 1992

Photoionization processes of TMPD in $H_2O$ and $D_2O$ were studied, by measuring steady-state absorption, emission, fluorescence excitation spectra, and fluorescence lifetimes on picosecond time scale. The steady-state absorption spectra showed that there exists a cation-ion pair (Wurster's Blue) in $H_2O$ and in $D_2O$ in the electronic ground state. Temperature and excitation wavelength dependence were also studied and the results show that the photoionization reaction in water is an activated process and the fluorescence lifetime is independent of the vibrational excess energy in the uv excitation range of 283-310 nm.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.434-437
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• 1991

Irradiation of 5-styryl-1,3-dimethyluracil (5-SDU) with 2,3-dimethyl-2-butene (DMB) gives a [4+2] cycloadduct which is converted into a [2+2] cycloadduct on the prolonged irradiation. Triplet sensitization, quenching, and external heavy atom effect on the [4+2] photocycloaddition reaction demonstrate the singlet pathway and salt effect excludes a radical ion pair precursor possibility. Polar solvents increase the reaction efficiency implying a polar exciplex involvement in the [4+2] photocycloaddition reaction. Inverse temperature dependence both on the reaction and DMB fluorescence quenching of 5-SDU indicates the presence of a singlet exciplex intermediate.